Antistatic Adhesive Optical Film and Image Display

ABSTRACT

The present invention aims at providing an antistatic pressure-sensitive adhesive optical film exhibiting excellent antistatic effect, optical properties, and water resistance and having excellent adhesion between the antistatic layer and the pressure-sensitive adhesive layer. An antistatic pressure-sensitive adhesive optical film, the optical film having an antistatic layer laminated on at least one side of the optical film, and a pressure-sensitive adhesive layer further laminated on the antistatic layer, wherein the antistatic layer comprises a conductive polymer and a sulfonic acid compound as raw material components, and the pressure-sensitive adhesive layer is formed of an acryl-based pressure-sensitive adhesive containing nitrogen.

TECHNICAL FIELD

The present invention relates to an antistatic pressure-sensitiveadhesive optical film having an antistatic layer laminated on at leastone side of an optical film, and having a pressure-sensitive adhesivelayer further laminated on the antistatic layer. Furthermore, it relatesto an image viewing display using the above-mentioned antistaticpressure-sensitive adhesive optical film, such as liquid crystaldisplays (LCDs), organic electroluminescence viewing displays, and PDPs.As the optical films, a polarizing plate, a retardation plate, anoptical compensation film, a brightness enhancement film, etc., andfurthermore optical films with the films laminated to each other may bementioned.

BACKGROUND ART

In liquid crystal displays etc., an image forming system necessarilyrequires polarizing elements disposed on both sides of a liquid crystalcell, and in general, polarizing plates are adhered thereto. Moreover,in liquid crystal panels, in order to improve display quality ofdisplays, various optical elements in addition to the polarizing platesare increasingly used. For example, retardation plates for prevention ofcoloring, viewing-angle expansion films for improving viewing angle ofliquid crystal displays, and furthermore, brightness enhancement filmsfor increasing contrast of displays etc. are used. These films aregenerically named and called optical films.

In these optical films, in order to prevent occurrence of damage andcontamination to a surface of the optical film in transportation ormanufacturing process until it is sent to consumers, surface protectivefilms are usually attached on a surface thereof. The surface protectivefilm is attached from a stage in which the optical film is in a state ofsingle substance, and in some case it is peeled after being attachedonto an LCD etc., and furthermore in other cases it is attached againafter peeled to a same or another surface protective film. And therehave been problems that static electricity generated incase of peelingof the surface protective film may destroy circuits, such as in LCDpanels. This static electricity affects array elements in the LCD paneland further affects alignment of the liquid crystal and induces problemsof defects. The surface protective film will give the same problems dueto friction of the optical films not only in peeling, but in themanufacturing process, or in the use by consumers. In order to solve theproblems, there has bee proposed application of antistatic property tooptical films, such as polarizing plate. For example, disclosed areoptical films with an antistatic layer having a layer provided on thesurface of the optical film, and optical films having a transparentconductive layer provided on one side or both sides of the opticalfilms.

When attaching an optical film on a liquid crystal cell,pressure-sensitive adhesives are usually used. Furthermore, in adhesionbetween optical films and liquid crystal cells or between optical films,each material are usually attached together using pressure-sensitiveadhesives in order to reduce loss of light. In such a case, sinceadvantages such as omission of drying step for fixing optical films maybe given, generally used is a pressure-sensitive adhesive optical filmhaving a pressure-sensitive adhesive layer beforehand provided on oneside of the optical film.

The pressure-sensitive adhesive optical films are cut into a size of adisplay in use. In the case of handling in use, touch of an edge (cutsection) of the pressure-sensitive adhesive optical film by operatorsand by apparatuses may cause possible lack of the pressure-sensitiveadhesive in the touched portion. Attachment of the pressure-sensitiveadhesive optical film having such lack of the pressure-sensitiveadhesive to the liquid crystal cells fails to provide proper adhesion inthe lack portion, and therefore, the portion gives reflection of light,causing possible problems of display defects. In particular, in thesedays, since narrower edges of displays are needed, even defects createdat the edges significantly reduce display quality. Furthermore, whenpeeling of the film from the panel is necessary due to inclusion offoreign matters, etc., after attachment of the pressure-sensitiveadhesive optical film to the liquid crystal panel, avoidance of troubleof residue of the pressure-sensitive adhesive (what is called adhesiveresidue phenomenon) around the side of the panel, that is, excellentreworkability will be needed.

And it is also proposed to provide antistatic property to theabove-described pressure-sensitive adhesive optical films. For example,it is proposed that antistatic property is provided to an antiglarelayer by inclusion of electric conductive particles in the antiglarelayer on the surface of a polarizing plate simultaneously having apressure-sensitive adhesive layer on an opposite side (Japanese PatentApplication Laid-Open No. 10-239521). However, the method in JapanesePatent Application Laid-Open No. 10-239521 has difficulty in maintenanceof physical property as an antiglare layer, and therefore shows limitedstability. In providing an antistatic layer to a pressure-sensitiveadhesive optical film, in order to cancel poor alignment of the liquidcrystal cell caused by application of a voltage that happens within thepanel, it is preferred to provide the antistatic layer between theoptical film and the pressure-sensitive adhesive layer. Antistaticpressure-sensitive adhesive optical films having an antistatic layerprovided between an optical film and a pressure-sensitive adhesive layerhas a problem of omission of a pressure-sensitive adhesive and adhesiveresidue, and a problem of reworkability. A method of inclusion ofconductive substances in a pressure-sensitive adhesive layer is proposedas a method of giving antistatic function to an optical film (JapanesePatent Application Laid-Open No. 2003-294951). However, the method inJapanese Patent Application Laid-Open No. 2003-294951 has difficulty inmaintenance of physical property as a pressure-sensitive adhesive layer,therefore shows limited stability.

SUMMARY OF THE INVENTION

The present invention aims at providing an antistatic pressure-sensitiveadhesive optical film exhibiting excellent antistatic effect, opticalproperties, and water resistance and having excellent adhesion betweenthe antistatic layer and the pressure-sensitive adhesive layer, whereinan antistatic layer is laminated on at least one side of a optical filmand a pressure-sensitive adhesive layer is further laminated on theantistatic layer. Furthermore, the present invention aims at providingan image viewing display using the antistatic pressure-sensitiveadhesive optical film.

As a result of repeated wholehearted investigation performed by thepresent inventors for solving the problem, it has been found out thatthe problem may be solved by the following antistatic pressure-sensitiveadhesive optical film, leading to completion of the present invention.

That is, the present invention relates to an antistaticpressure-sensitive adhesive optical film, the optical film having anantistatic layer laminated on at least one side of a optical film, and apressure-sensitive adhesive layer further laminated on the antistaticlayer, wherein the antistatic layer includes a conductive polymer and asulfonic acid compound as raw material components, and thepressure-sensitive adhesive layer is formed of an acryl-basedpressure-sensitive adhesive including nitrogen.

An antistatic pressure-sensitive adhesive optical film exhibitingexcellent antistatic effect, optical properties, and water resistance,and having excellent adhesive property between the antistatic layer andthe pressure-sensitive adhesive layer may be provided by disposing anantistatic layer including a conductive polymer and a sulfonic acidcompound as raw material components between the optical film and thepressure-sensitive adhesive layer, and by forming the pressure-sensitiveadhesive layer with an acryl-based pressure-sensitive adhesivecontaining nitrogen.

Specifically, an antistatic layer formed between the optical film andthe pressure-sensitive adhesive layer exhibits excellent antistaticeffect, and can suppress generation of static electricity by peeling ofa surface protective film or by friction of optical films, leading toprevention of breakage of circuits, or of alignment defects of liquidcrystals. Furthermore, since a sulfonic acid compound (dopant) is usedwith the conductive polymer as a raw material component of theantistatic layer, reaction of apart of the conductive polymer and thesulfonic acid compound forms a sulfonate. It is probable that thissulfonate works to improve the conductivity of the antistatic layer.Although, in case of addition of sulfonic acid compound as a dopant,conventional pressure-sensitive adhesive layers consisting ofacryl-based pressure-sensitive adhesives induced problems in adhesiveproperties of the antistatic layer and the pressure-sensitive adhesivelayer, it was found out that use of acryl-based pressure-sensitiveadhesives containing nitrogen can improve the adhesive propertiesbetween the both layers. Thereby, missing of some of thepressure-sensitive adhesive caused by contact between film ends duringhandling of the antistatic pressure-sensitive adhesive optical film, andadhesive residue at the time of reworking of the liquid crystal panelscan be greatly reduced, resulting in improvement in the handlingproperty of the antistatic pressure-sensitive adhesive optical film orin the optical property of the optical film.

The conductive polymer is preferably water soluble or water dispersible.This water soluble or water dispersible conductive polymer is preferablyof polythiophene-based conductive polymer.

In addition, the base polymer of the acryl-based pressure-sensitiveadhesives containing nitrogen is preferably a copolymer of a monomercontaining nitrogen and an acryl-based monomer, or a mixture of apolymer containing nitrogen and an acryl-based polymer.

The present invention relates to an image viewing display that uses atleast one sheet of the antistatic pressure-sensitive adhesive opticalfilm. In use of the antistatic pressure-sensitive adhesive optical filmof the present invention, one of the film may be used independently ortwo or more of the films may be used in combination according to variouskinds of use of the image viewing displays, such as liquid crystalviewing displays.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates an example of a cross section of an antistaticpressure-sensitive adhesive optical film of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As illustrated in FIG. 1, in an antistatic pressure-sensitive adhesiveoptical film of the present invention, an antistatic layer 2 and apressure-sensitive adhesive layer 3 are laminated on one side of anoptical film 1 in this order. In FIG. 1, the pressure-sensitive adhesivelayer 3 is formed on one side of the optical film 1, however, thepressure-sensitive adhesive layer 3 may be formed on both sides of theoptical film. In addition, the pressure-sensitive adhesive layer 3 onanother side may have an antistatic layer 2.

The antistatic layer 2 of the antistatic pressure-sensitive adhesiveoptical film according to the present invention includes a conductivepolymer that is an antistatic agent, and a sulfonic acid compound thatis a dopant, as a raw material component.

Conductive polymers having excellent optical properties, externalappearance and antistatic effect, and having excellent stability of theantistatic effect in a heated condition and in a humidified conditionare used as conductive polymers. Such conductive polymers includepolymers, such as polyaniline, polythiophene, polypyrrole, andpolyquinoxaline. Of these polymers, polyaniline, polythiophene, etc.that easily become water-soluble conductive polymers or waterdispersible conductive polymers are preferably used. In particular,polythiophene is preferred.

Use of the water soluble conductive polymer or water dispersibleconductive polymer allows preparation of an application liquid informing an antistatic layer as an aqueous solution or a waterdispersion, and can not require use of organic solvents in theapplication liquid, and thereby can suppress deterioration anddegradation of base materials of the optical film caused by the organicsolvents. It is preferred, from the point of adhesion, to use only wateras solvents for the aqueous solution or water dispersion, buthydrophilic solvents may also be included. The hydrophilic solventsinclude, for example, alcohols, such as methanol, ethanol, n-propanol,isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amylalcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol,1-ethyl-1-propanol, 2-methyl-l-butanol, n-hexanol, cyclohexanol, etc.

The weight average molecular weight expressed in terms of polystyrene ofthe water soluble or water dispersible polyaniline is preferably 500000or less, and more preferably 300000 or less. The weight averagemolecular weight expressed in terms of polystyrene of the water solubleor water dispersible polythiophene is preferably 400000 or less, andmore preferably 300000 or less. The weight average molecular weightexceeding the value cannot likely satisfy the water solubility or waterdispersibility. Preparation of the application liquid (aqueous solutionor water dispersion) by use of such polymer tends to make solid contentof polymer remain in the application liquid, or to give the applicationliquid having a higher viscosity, leading to difficulty of formation ofan antistatic layer with a uniform thickness.

The water solubility of the water soluble electric conductive polymerrepresents a water solubility having 5 g or more of solubility to 100 gof water. The solubility of the electric conductive polymer to 100 g ofwater is preferably 20 to 30 g. The water dispersible conductive polymeris a polymer that allows dispersion of conductive polymers, such aspolyaniline and polythiophene in a particle-shaped state in water, andthe water dispersion has a lower viscosity of liquid, can provide easyformation of a thinner film, and further enables a uniform appliedlayer. Here, from the view point of the uniformity of the antistaticlayer, the size of 1 μm or less of the particles is preferred.

Furthermore, it is preferred that the water soluble conductive polymeror water dispersible conductive polymer, such as polyaniline andpolythiophene as described above, have hydrophilic functional group inthe molecule thereof. The hydrophilic functional groups include, forexample, a sulfone group, amino group, amido group, imino group,quaternary-ammonium-salt group, hydroxyl group, mercapto group,hydrazino group, carboxyl group, sulfate group, phosphoric ester group,or salts of the above-mentioned groups, etc. Inclusion of thehydrophilic functional group in the molecule improves solubility towater, or allows easy dispersion in a particle shape in water, leadingto easier preparation of the water soluble conductive polymer or waterdispersible conductive polymer.

As examples of commercially available water soluble conductive polymers,a polyaniline sulfonic acid (manufactured by Mitsubishi Rayon Co., Ltd.,weight average molecular weight expressed in terms of polystyrene150000) etc. may be mentioned. As examples of commercially availablewater dispersible conductive polymers, a polythiophene based conductivepolymer (manufactured by Nagase Chemtech Co., Ltd., trade name, Denatronseries) etc. maybe mentioned.

The sulfonic acid compounds include, for example, p-toluenesulfonicacid, benzenesulfonic acid, ethylbenzene sulfonic acid,octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, mesitylenesulfonic acid, m-xylene sulfonic acid, polystyrene sulfonic acid,polyvinyl sulfonic acid, etc. These may be used independently and two ormore kinds may be used in combination. In preparation of the aqueousapplication liquid using the water soluble conductive polymer or thewater dispersible conductive polymer described above, it is preferred touse water soluble sulfonic acid compounds, such as polystyrene sulfonicacid and polyvinyl sulfonic acid, for improvement in solubility ordispersibility of the conductive polymer.

An amount of 100 to 300 parts by weight of the sulfonic acid compoundwith respect to 100 parts by weight of the conductive polymer ispreferably used, and more preferably 150 to 250 parts by weight. Theamount of addition of the sulfonic acid compound less than 100 parts byweight gives less amount of the sulfonate formed by reaction of theconductive polymer and the sulfonic acid compound, and tends to provideinsufficient antistatic function, or insufficient improvement effect ofthe adhesion between the antistatic layer and the pressure-sensitiveadhesive layer. On the other hand, the amount of addition exceeding 300parts by weight substantially tends not to provide effects on theantistatic function, and on the adhesion between the antistatic layerand the pressure-sensitive adhesive layer.

Binder components may be used, in combination, in formation materials ofthe antistatic layer for the purpose of improvement of film-formingproperty of the antistatic agent, and adhesion with respect to theoptical film, etc. In use of the water soluble conductive polymer or thewater dispersible conductive polymer as an antistatic agent, it ispreferred to use water soluble or water dispersible binder components.The binder components include, for example, polyurethane-based resins,polyester-based resins, acryl-based resins, polyether-based resins,cellulose-based resins, polyvinyl alcohol-based resins, epoxy resins,polyvinyl pyrrolidones, polystyrene-based resins, polyethylene glycol,pentaerythritol, etc. Polyurethane-based resins, polyester-based resins,and acryl-based resins are especially preferred. These binder componentsmay be suitably used independently, and two or more kinds may be used incombination according to usages. Although dependent on kinds ofconductive polymers, the amount of the binder component used is usually20 to 5000 parts by weight with respect to 100 parts by weight of theconductive polymer, and preferably 50 to 1500 parts by weight.

The surface electric resistance value of the antistatic layer ispreferably 1×10¹² Ω/square or less, and more preferably 1×10¹¹ Ω/squareor less. The surface electric resistance value exceeding 1×10¹²Ω/squarecannot exhibit sufficient antistatic function. Therefore, it causespeeling of the surface protective film, generates static electricity byfriction of the optical film, and possibly causes electrification toinduce breakage of circuits of the liquid crystal cell and alignmentdefect of the liquid crystal.

As a pressure-sensitive adhesive for forming a pressure-sensitiveadhesive layer 3 of an antistatic pressure-sensitive adhesive opticalfilm according to the present invention, an acryl-basedpressure-sensitive adhesives containing nitrogen is used. Theacryl-based pressure-sensitive adhesive has excellent opticaltransparency, exhibits suitable pressure-sensitive adhesive propertiessuch as wettability, cohesiveness, and adhesion, and has excellentweather resistance, heat-resisting property, etc.

The base polymer of the acryl-based pressure-sensitive adhesivescontaining nitrogen is preferably made of copolymers (acrylic polymercontaining nitrogen) of monomers containing nitrogen and acryl-basedmonomer or of a mixture of polymer containing nitrogen and acryl-basedpolymer.

The monomer containing nitrogen in particular will not be limited aslong as they are vinyl monomers containing a nitrogen atom, and examplesthereof include, for example, maleimide, N-vinyl pyrrolidone, primaryamines, secondary amines, tertiary amines, and quaternary ammonium saltsof (meth) acryl-based monomer, and (meth) acrylamide, etc. Specifically,examples thereof include N-cyclohexylmaleimide, N-phenylmaleimide,N-acryloyl morpholine, N,N-(dimethylamino)ethyl(meth)acrylate,N,N-(dimethylamino)propyl(meth)acrylate, 3-(3-pyridinyl)propyl(meth)acrylate, N,N-dimethyl(meth)acrylamide,N,N-diethyl(meth)acrylamide, N-methyl(meth)acrylamide,N-ethyl(meth)acrylamide, and N-hexyl(meth)acrylamide, etc. These may beindependently used and two or more kinds may be used in combination.

Alkyl (meth)acrylates having alkyl groups with 4 to 12 carbon atoms aresuitably used as an acryl-based monomer. Specifically, the acryl-basedmonomer includes butyl (meth) acrylate, 2-ethylhexyl (meth)acrylate,isooctyl methacrylate, n-octyl (meth)acrylate, isononyl (meth)acrylate,lauryl (meth)acrylate, etc. These may be independently used and two ormore kinds may be used in combination.

In the case of acryl-based polymer containing nitrogen, copolymerizationof 0.5 to 50 parts by weight of a monomer containing nitrogen withrespect to 100 parts by weight of the alkyl (meth)acrylate is preferred,and more preferably 1 to 30 parts by weight. The copolymerization of themonomer containing nitrogen less than 0.5 parts by weight tends not tosufficiently improve the adhesion between the antistatic layer and thepressure-sensitive adhesive layer, and on the other hand, thecopolymerization of the monomer exceeding 50 parts by weight tends tomake initial adhesion poorer.

For the purpose of improvement of adherability and heat-resistance, oneor more kinds of various monomers may be introduced into the acryl-basedpolymer containing nitrogen by copolymerization. Examples of suchmonomers for copolymerization include, for example, monomers containinga hydroxyl group, such as 2-hydroxyethyl(meth)acrylate,2-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate,6-hydroxyhexyl(meth)acrylate, 8-hydroxyoctyl(meth)acrylate,10-hydroxydecyl(meth)acrylate, 12-hydroxylauryl(meth)acrylate,(4-hydroxymethylcyclohexyl)-methyl acrylate, etc.; monomers containing acarboxyl group such as (meth)acryl-based acid, carboxyethyl (meth)acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid,fumaric acid, crotonic acid, etc.; monomers containing an acid anhydridegroup, such as maleic anhydride and itaconic acid anhydride;caprolactone additive of acrylic acid; monomers containing a sulfonicacid group, such as styrene sulfonic acid, allylsulfonic acid,sulfopropyl (meth)acrylate, (meth)acryloyloxy naphthalenesulfonic acid,etc.; monomers containing a phosphoric acid group, such as2-hydroxyethyl acryloyl phosphate, etc.

Furthermore, examples of such monomers for copolymerization alsoinclude, vinyl-based monomers such as vinyl acetate, vinyl propionate,styrene, and α-methyl styrene; acryl-based monomers containing an epoxygroup such as glycidyl (meth)acrylate; glycol-based acrylate monomerssuch as polyethylene glycol (meth)acrylate, polypropylene glycol(meth)acrylate, methoxyethylene glycol (meth) acrylate,methoxypolypropylene glycol (meth)acrylate etc.; acrylate-based monomerssuch as tetrahydrofurfuryl (meth)acrylate, fluorinated (meth)acrylate,silicone (meth)acrylate, 2-methoxy ethyl acrylate, etc.

Of these polymers, in view of adherability to liquid crystal cells andadhesive durability as optical film usages, monomers containing acarboxyl group, such as acrylic acid, are preferably used.

The proportion of the copolymerization monomer in the acryl-basedpolymer containing nitrogen is not in particular limited, and it ispreferably approximately 0.1 to 10% in weight ratio.

An average molecular weight of the acryl-based polymer containingnitrogen is not especially limited, and the weight average molecularweight is preferably approximately 300000 to 2500000. The acryl-basedpolymer containing nitrogen may be produced by various publicly knownmethods, and for example radical-polymerization methods, such as bulkpolymerization method, solution-polymerization method, andsuspension-polymerization method, may be suitably selected. As radicalpolymerization initiators, various kinds of publicly known initiators,such as an azo-based and peroxide-based initiator, may be used. Reactiontemperature is usually approximately 50 to 80° C., and reaction periodis 1 to 8 hours. Furthermore, of the manufacturing methods, thesolution-polymerization method is preferred and, generally ethylacetate, toluene, etc. are used as a solvent. The solution concentrationis usually approximately 20 to 80% by weight.

The base polymer of the acryl-based pressure-sensitive adhesivescontaining nitrogen may be a mixture of a polymer containing nitrogenobtained by polymerization of the monomer containing nitrogen (and amonomer for copolymerization), and an acryl-based polymer obtained bypolymerization of the acryl-based monomer (and a monomer forcopolymerization).

The polymer containing nitrogen is preferably 0.5 to 50 parts by weightwith respect to 100 parts by weight of the acryl-based polymer, and morepreferably 1 to 30 parts by weight. The polymer containing nitrogen lessthan 0.5 parts by weight tends not sufficiently to improve adhesionbetween the antistatic layer and the pressure-sensitive adhesive layer,and on the other hand, the polymer containing nitrogen exceeding 50parts by weight tends to give poor initial adhesion.

The pressure-sensitive adhesive is preferably a pressure-sensitiveadhesive composition including cross linking agents. Multifunctionalcompounds that can be blended with the pressure-sensitive adhesiveinclude organic cross linking agents and polyfunctional metal chelates.The organic cross linking agents include epoxy-based cross linkingagents, isocyanate-based cross linking agents, imine-based cross linkingagents, etc. As organic cross linking agents, isocyanate-based crosslinking agents are preferred. Polyfunctional metal chelates are obtainedby covalent bonding or coordinate bonding polyvalent metals with organiccompounds. The polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe,Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. Atoms inthe organic compounds capable of covalent bonding or coordinate bondinginclude an oxygen atom, etc., and the organic compounds include alkylesters, alcohol compounds, carboxylic acid compounds, ether compounds,ketone compounds, etc.

The proportion of blending of the base polymer and the cross linkingagent is not in particular limited, and the cross linking agent (solidcontent) is preferably approximately 0.01 to 10 parts by weight withrespect to 100 parts by weight of the base polymer (solid content), andmore preferably approximately 0.1 to 5 parts by weight.

Furthermore, various kinds of additives such as tackifiers,plasticizers, fillers including glass fibers, glass beads, metalpowders, other inorganic powders, pigments, colorants, fillers,antioxidants, ultraviolet absorbers, silane coupling agents, etc. mayalso be suitably used as the pressure-sensitive adhesive, if needed, inthe range that does not depart from objects of the present invention.The pressure-sensitive adhesive may also be used as a pressure-sensitiveadhesive layer exhibiting light diffusibility by inclusion of particles.

As optical film 1 used for the antistatic pressure-sensitive adhesiveoptical film of the present invention, optical films used for formationof image viewing displays, such as liquid crystal viewing displays, maybe used, and the kind is not limited in particular. For example,polarizing plates maybe illustrated as the optical films. Polarizingplates having a transparent protective film one side or both sides of apolarizer is generally used.

A polarizer is not limited especially but various kinds of polarizer maybe used. As a polarizer, for example, a film that is uniaxiallystretched after having dichromatic substances, such as iodine anddichromatic dye, absorbed to hydrophilic high molecular weight polymerfilms, such as polyvinyl alcohol type film, partially formalizedpolyvinyl alcohol type film, and ethylene-vinyl acetate copolymer typepartially saponified film; poly-ene type orientation films, such asdehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride,etc. may be mentioned. In these, a polyvinyl alcohol type film on whichdichromatic materials (iodine, dyes) is absorbed and oriented afterstretched is suitably used. Although thickness of polarizer is notespecially limited, the thickness of about 5 to 80 μm is commonlyadopted.

A polarizer that is uniaxially stretched after a polyvinyl alcohol typefilm dyed with iodine is obtained by stretching a polyvinyl alcohol filmby 3 to 7 times the original length, after dipped and dyed in aqueoussolution of iodine. If needed the film may also be dipped in aqueoussolutions, such as boric acid and potassium iodide, which may includezinc sulfate, zinc chloride. Furthermore, before dyeing, the polyvinylalcohol type film may be dipped in water and rinsed if needed. Byrinsing polyvinyl alcohol type film with water, effect of preventingun-uniformity, such as unevenness of dyeing, is expected by makingpolyvinyl alcohol type film swelled in addition that also soils andblocking inhibitors on the polyvinyl alcohol type film surface may bewashed off. Stretching may be applied after dyed with iodine or may beapplied concurrently, or conversely dyeing with iodine may be appliedafter stretching. Stretching is applicable in aqueous solutions, such asboric acid and potassium iodide, and in water bath.

As the protective film prepared on one side or both sides of thepolarizer, materials is excellent in transparency, mechanical strength,heat stability, water shielding property, isotropy, etc. may bepreferably used. As materials of the above-mentioned protective layer,for example, polyester type polymers, such as polyethylene terephthalateand polyethylenenaphthalate; cellulose type polymers, such as diacetylcellulose and triacetyl cellulose; acrylics type polymer, such as polymethylmethacrylate; styrene type polymers, such as polystyrene andacrylonitrile-styrene copolymer (AS resin); polycarbonate type polymermay be mentioned. Besides, as examples of the polymer forming aprotective film, polyolefin type polymers, such as polyethylene,polypropylene, polyolefin that has cyclo-type or norbornene structure,ethylene-propylene copolymer; vinyl chloride type polymer; amide typepolymers, such as nylon and aromatic polyamide; imide type polymers;sulfone type polymers; polyether sulfone type polymers; polyether-etherketone type polymers; poly phenylene sulfide type polymers; vinylalcohol type polymer; vinylidene chloride type polymers; vinyl butyraltype polymers; allylate type polymers; polyoxymethylene type polymers;epoxy type polymers; or blend polymers of the above-mentioned polymersmay be mentioned. Films made of heat curing type or ultraviolet raycuring type resins, such as acryl based, urethane based, acryl urethanebased, epoxy based, and silicone based, etc. may be mentioned.

Moreover, as is described in Japanese Patent Laid-Open Publication No.2001-343529 (WO01/37007), polymer films, for example, resin compositionsincluding (A) thermoplastic resins having substituted and/ornon-substituted imido group is in side chain, and (B) thermoplasticresins having substituted and/or non-substituted phenyl and nitrilegroup in side chain may be mentioned. As an illustrative example, a filmmay be mentioned that is made of a resin composition includingalternating copolymer comprising iso-butylene and N-methyl maleimide,and acrylonitrile-styrene copolymer. A film comprising mixture extrudedarticle of resin compositions etc. may be used.

In general, a thickness of the protection film, which can be determinedarbitrarily, is 1 through 500 μm, preferably 5 through 200 μm inviewpoint of strength, work handling and thin layer.

Moreover, it is preferable that the protective film may have as littlecoloring as possible. Accordingly, a protective film having a phasedifference value in a film thickness direction represented byRth=[(nx+ny)/2−nz]×d of −90 nm through +75 nm (where, nx and nyrepresent principal indices of refraction in a film plane, nz representsrefractive index in a film thickness direction, and d represents a filmthickness) may be preferably used. Thus, coloring (optical coloring) ofpolarizing plate resulting from a protective film may mostly becancelled using a protective film having a phase difference value (Rth)of −90 nm through +75 nm in a thickness direction. The phase differencevalue (Rth) in a thickness direction is preferably −80 nm through +60nm, and especially preferably −70 nm through +45 nm.

As a protective film, if polarization property and durability are takeninto consideration, cellulose based polymer, such as triacetylcellulose, is preferable, and especially triacetyl cellulose film issuitable. In addition, when the protective films are provided on bothsides of the polarizer, the protective films comprising same polymermaterial may be used on both of a front side and a back side, and theprotective films comprising different polymer materials etc. maybe used.Adhesives are used for adhesion processing of the above describedpolarizer and the protective film. As adhesives, isocyanate derivedadhesives, polyvinyl alcohol derived adhesives, gelatin derivedadhesives, vinyl polymers derived latex type, aqueous polyurethane basedadhesives, aqueous polyesters derived adhesives, etc. may be mentioned.

A hard coat layer may be prepared, or antireflection processing,processing aiming at sticking prevention, diffusion or anti glare may beperformed onto the face on which the polarizing film of the abovedescribed protective film has not been adhered.

A hard coat processing is applied for the purpose of protecting thesurface of the polarizing plate from damage, and this hard coat film maybe formed by a method in which, for example, a curable coated film withexcellent hardness, slide property etc. is added on the surface of theprotective film using suitable ultraviolet curable type resins, such asacrylic type and silicone type resins. Anti reflection processing isapplied for the purpose of antireflection of outdoor daylight on thesurface of a polarizing plate and it may be prepared by forming anantireflection film according to the conventional method etc. Besides, asticking prevention processing is applied for the purpose of adherenceprevention with adjoining layer.

In addition, an anti glare processing is applied in order to prevent adisadvantage that outdoor daylight reflects on the surface of apolarizing plate to disturb visual recognition of transmitting lightthrough the polarizing plate, and the processing may be applied, forexample, by giving a fine concavo-convex structure to a surface of theprotective film using, for example, a suitable method, such as roughsurfacing treatment method by sandblasting or embossing and a method ofcombining transparent fine particle. As a fine particle combined inorder to form a fine concavo-convex structure on the above-mentionedsurface, transparent fine particles whose average particle size is 0.5to 50 μm, for example, such as inorganic type fine particles that mayhave conductivity comprising silica, alumina, titania, zirconia,tinoxides, indiumoxides, cadmiumoxides, antimony oxides, etc., andorganic type fine particles comprising cross-linked of non-cross-linkedpolymers may be used. When forming fine concavo-convex structure on thesurface, the amount of fine particle used is usually about 2 to 50weight part to the transparent resin 100 weight part that forms the fineconcavo-convex structure on the surface, and preferably 5 to 25 weightpart. An anti glare layer may serve as a diffusion layer (viewing angleexpanding function etc.) for diffusing transmitting light through thepolarizing plate and expanding a viewing angle etc.

In addition, the above-mentioned antireflection layer, stickingprevention layer, diffusion layer, anti glare layer, etc. maybe built inthe protective film itself, and also they maybe prepared as an opticallayer different from the protective layer.

An optical film of the present invention is especially no limitationabout the optical layers, which may be used for formation of a liquidcrystal display etc., such as a reflector, a transflective plate, aretardation plate (a half wavelength plate and a quarter wavelengthplate included), and a viewing angle compensation film, may be used.

Especially preferable polarizing plates are; a reflection typepolarizing plate or a transflective type polarizing plate in which areflector or a transflective reflector is further laminated onto apolarizing plate of the present invention; an elliptically polarizingplate or a circular polarizing plate in which a retardation plate isfurther laminated onto the polarizing plate; a wide viewing anglepolarizing plate in which a viewing angle compensation film is furtherlaminated onto the polarizing plate; or a polarizing plate in which abrightness enhancement film is further laminated onto the polarizingplate.

A reflective layer is prepared on a polarizing plate to give areflection type polarizing plate, and this type of plate is used for aliquid crystal display in which an incident light from a view side(display side) is reflected to give a display. This type of plate doesnot require built-in light sources, such as a backlight, but has anadvantage that a liquid crystal display may easily be made thinner. Areflection type polarizing plate may be formed using suitable methods,such as a method in which a reflective layer of metal etc. is, ifrequired, attached to one side of a polarizing plate through atransparent protective layer etc.

As an example of a reflection type polarizing plate, a plate may bementioned on which, if required, a reflective layer is formed using amethod of attaching a foil and vapor deposition film of reflectivemetals, such as aluminum, to one side of a matte treated protectivefilm. Moreover, a different type of plate with a fine concavo-convexstructure on the surface obtained by mixing fine particle into theabove-mentioned protective film, on which a reflective layer ofconcavo-convex structure is prepared, may be mentioned. The reflectivelayer that has the above-mentioned fine concavo-convex structurediffuses incident light by random reflection to prevent directivity andglaring appearance, and has an advantage of controlling unevenness oflight and darkness etc. Moreover, the protective film containing thefine particle has an advantage that unevenness of light and darkness maybe controlled more effectively, as a result that an incident light andits reflected light that is transmitted through the film are diffused. Areflective layer with fine concavo-convex structure on the surfaceeffected by a surface fine concavo-convex structure of a protective filmmay be formed by a method of attaching a metal to the surface of atransparent protective layer directly using, for example, suitablemethods of a vacuum evaporation method, such as a vacuum depositionmethod, an ion plating method, and a sputtering method, and a platingmethod etc.

Instead of a method in which a reflection plate is directly given to theprotective film of the above-mentioned polarizing plate, a reflectionplate may also be used as a reflective sheet constituted by preparing areflective layer on the suitable film for the transparent film. Inaddition, since a reflective layer is usually made of metal, it isdesirable that the reflective side is covered with a protective film ora polarizing plate etc. when used, from a view point of preventingdeterioration in reflectance by oxidation, of maintaining an initialreflectance for a long period of time and of avoiding preparation of aprotective layer separately etc.

In addition, a transflective type polarizing plate may be obtained bypreparing the above-mentioned reflective layer as a transflective typereflective layer, such as a half-mirror etc. that reflects and transmitslight. A transflective type polarizing plate is usually prepared in thebackside of a liquid crystal cell and it may form a liquid crystaldisplay unit of a type in which a picture is displayed by an incidentlight reflected from a view side (display side) when used in acomparatively well-lighted atmosphere. And this unit displays a picture,in a comparatively dark atmosphere, using embedded type light sources,such as a back light built in backside of a transflective typepolarizing plate. That is, the transflective type polarizing plate isuseful to obtain of a liquid crystal display of the type that savesenergy of light sources, such as a back light, in a well-lightedatmosphere, and can be used with a built-in light source if needed in acomparatively dark atmosphere etc.

The above-mentioned polarizing plate maybe used as ellipticallypolarizing plate or circularly polarizing plate on which the retardationplate is laminated. A description of the above-mentioned ellipticallypolarizing plate or circularly polarizing plate will be made in thefollowing paragraph. These polarizing plates change linearly polarizedlight into elliptically polarized light or circularly polarized light,elliptically polarized light or circularly polarized light into linearlypolarized light or change the polarization direction of linearlypolarization by a function of the retardation plate. As a retardationplate that changes circularly polarized light into linearly polarizedlight or linearly polarized light into circularly polarized light, whatis called a quarter wavelength plate (also called λ/4 plate) is used.Usually, half-wavelength plate (also called λ/2 plate) is used, whenchanging the polarization direction of linearly polarized light.

Elliptically polarizing plate is effectively used to give a monochromedisplay without above-mentioned coloring by compensating (preventing)coloring (blue or yellow color) produced by birefringence of a liquidcrystal layer of a super twisted nematic (STN) type liquid crystaldisplay. Furthermore, a polarizing plate in which three-dimensionalrefractive index is controlled may also preferably compensate (prevent)coloring produced when a screen of a liquid crystal display is viewedfrom an oblique direction. Circularly polarizing plate is effectivelyused, for example, when adjusting a color tone of a picture of areflection type liquid crystal display that provides a colored picture,and it also has function of antireflection.

As retardation plates, birefringent films obtained by uniaxially orbiaxially stretched polymer materials, oriented films of liquid crystalpolymers, oriented layers of liquid crystal polymers currently supportedwith films may be mentioned. A thickness of the retardation plate isalso not especially limited, and it is about 20 to 150 μm in general.

As polymer material, for example, there may be mentioned: polyvinylalcohols, polyvinyl butyrals, polymethyl vinyl ethers, polyhydroxy ethylacrylates, hydroxyethyl celluloses, hydroxypropyl celluloses, methylcelluloses, polycarbonates, polyallylates, polysulfones, polyethyleneterephthalates, polyethylene naphthalates, polyethersulfones,polyphenylene sulfides, polyphenylene oxides, polyallyl sulfones,polyamides, polyimides, polyolefins, polyvinyl chlorides, cellulose typepolymers, and norbornene based resins, or binary or ternary copolymers,graft copolymers, and blend object thereof. These polymer materials arestretched to obtain an oriented object that is stretched film.

As liquid crystalline polymers, for example, various kinds of polymersof principal chain type and side chain type in which conjugated linearatomic groups (mesogens) conferring liquid crystalline orientation areintroduced into a principal chain and a side chain of a polymer may bementioned. As examples of principal chain type liquid crystallinepolymers, polymers having a structure where mesogen groups are bonded byspacer parts conferring flexibility, for example, polyester based liquidcrystalline polymers having nematic orientation property, discoticpolymers, cholesteric polymers, etc. may be mentioned. As examples ofside chain type liquid crystalline polymers, polymers havingpolysiloxanes, polyacrylates, polymethacrylates, or polymalonates as aprincipal chain skeleton, and having mesogen parts comprisingpara-substituted cyclic compound units conferring nematic orientationproperty as side chains via spacer parts comprising conjugated atomicgroups may be mentioned. These liquid crystal polymer, for example, isaligned by developing a solution of a liquid crystal polymer on anorientation treated surface where rubbing treatment was performed to asurface of thin films, such as polyimide and polyvinyl alcohol, formedon a glass plate, or where silicon oxide is deposited by an obliqueevaporation method, and then by heat-treating.

Retardation plates that have suitable phase difference depending on thepurpose of use, such as aiming at compensation of coloring or viewingangle using birefringence, for example, various wavelength plates andliquid crystal layers, maybe used. In addition retardation plates inwhich two or more kinds of retardation plates are laminated together tocontrol optical properties, such as phase difference may be used.

The above-mentioned elliptically polarizing plate and an above-mentionedreflected type elliptically polarizing plate are laminated platecombining suitably a polarizing plate or a reflection type polarizingplate with a retardation plate. This type of elliptically polarizingplate etc. may be manufactured by combining a polarizing plate(reflected type) and a retardation plate, and by laminating them one byone separately in the manufacture process of a liquid crystal display.On the other hand, the polarizing plate in which lamination wasbeforehand carried out and was obtained as an optical film, such as anelliptically polarizing plate, is excellent in a stable quality, aworkability in lamination etc., and has an advantage in improvedmanufacturing efficiency of a liquid crystal display.

A viewing angle compensation film is a film for extending viewing angleso that a picture may look comparatively clearly, even when it is viewedfrom an oblique direction not from vertical direction to a screen. Assuch a viewing angle compensation retardation plate, in addition, a filmhaving birefringence property that is processed by uniaxial stretchingor orthogonal biaxial stretching and a bi-directional stretched film asinclined orientation film etc. may be used. As inclined orientationfilm, for example, a film obtained using a method in which a heatshrinking film is adhered to a polymer film, and then the combined filmis heated and stretched or shrinked under a condition of beinginfluenced by a shrinking force, or a film that is oriented in obliquedirection may be mentioned. The viewing angle compensation film issuitably combined for the purpose of prevention of coloring caused bychange of visible angle based on retardation by liquid crystal cell etc.and of expansion of viewing angle with good visibility.

Besides, a compensation plate in which an optical anisotropy layerconsisting of an alignment layer of liquid crystal polymer, especiallyconsisting of an inclined alignment layer of discotic liquid crystalpolymer is supported with triacetyl cellulose film may preferably beused from a viewpoint of attaining a wide viewing angle with goodvisibility.

The polarizing plate with which a polarizing plate and a brightnessenhancement film are adhered together is usually used being prepared ina backside of a liquid crystal cell. A brightness enhancement film showsa characteristic that reflects linearly polarized light with apredetermined polarization axis, or circularly polarized light with apredetermined direction, and that transmits other light, when naturallight by back lights of a liquid crystal display or by reflection from aback-side etc., comes in. The polarizing plate, which is obtained bylaminating a brightness enhancement film to a polarizing plate, thusdoes not transmit light without the predetermined polarization state andreflects it, while obtaining transmitted light with the predeterminedpolarization state by accepting a light from light sources, such as abacklight. This polarizing plate makes the light reflected by thebrightness enhancement film further reversed through the reflectivelayer prepared in the backside and forces the light re-enter into thebrightness enhancement film, and increases the quantity of thetransmitted light through the brightness enhancement film bytransmitting apart or all of the light as light with the predeterminedpolarization state. The polarizing plate simultaneously suppliespolarized light that is difficult to be absorbed in a polarizer, andincreases the quantity of the light usable for a liquid crystal picturedisplay etc., and as a result luminosity may be improved. That is, inthe case where the light enters through a polarizer from backside of aliquid crystal cell by the back light etc. without using a brightnessenhancement film, most of the light, with a polarization directiondifferent from the polarization axis of a polarizer, is absorbed by thepolarizer, and does not transmit through the polarizer. This means thatalthough influenced with the characteristics of the polarizer used,about 50 percent of light is absorbed by the polarizer, the quantity ofthe light usable for a liquid crystal picture display etc. decreases somuch, and a resulting picture displayed becomes dark. A brightnessenhancement film does not enter the light with the polarizing directionabsorbed by the polarizer into the polarizer but reflects the light onceby the brightness enhancement film, and further makes the light reversedthrough the reflective layer etc. prepared in the backside to re-enterthe light into the brightness enhancement film. By this above-mentionedrepeated operation, only when the polarization direction of the lightreflected and reversed between the both becomes to have the polarizationdirection which may pass a polarizer, the brightness enhancement filmtransmits the light to supply it to the polarizer. As a result, thelight from a backlight may be efficiently used for the display of thepicture of a liquid crystal display to obtain a bright screen.

A diffusion plate may also be prepared between brightness enhancementfilm and the above described reflective layer, etc. A polarized lightreflected by the brightness enhancement film goes to the above describedreflective layer etc., and the diffusion plate installed diffusespassing light uniformly and changes the light state into depolarizationat the same time. That is, the diffusion plate returns polarized lightto natural light state. Steps are repeated where light, in theunpolarized state, i.e., natural light state, reflects throughreflective layer and the like, and again goes into brightnessenhancement film through diffusion plate toward reflective layer and thelike. Diffusion plate that returns polarized light to the natural lightstate is installed between brightness enhancement film and the abovedescribed reflective layer, and the like, in this way, and thus auniform and bright screen may be provided while maintaining brightnessof display screen, and simultaneously controlling non-uniformity ofbrightness of the display screen. By preparing such diffusion plate, itis considered that number of repetition times of reflection of a firstincident light increases with sufficient degree to provide uniform andbright display screen conjointly with diffusion function of thediffusion plate.

The suitable films are used as the above-mentioned brightnessenhancement film. Namely, multilayer thin film of a dielectricsubstance; a laminated film that has the characteristics of transmittinga linearly polarized light with a predetermined polarizing axis, and ofreflecting other light, such as the multilayer laminated film of thethin film having a different refractive-index anisotropy (D-BEF andothers manufactured by 3M Co., Ltd.); an aligned film of cholestericliquid-crystal polymer; a film that has the characteristics ofreflecting a circularly polarized light with either left-handed orright-handed rotation and transmitting other light, such as a film onwhich the aligned cholesteric liquid crystal layer is supported (PCF350manufactured by NITTO DENKO CORPORATION, Transmax manufactured by MerckCo., Ltd., and others); etc. may be mentioned.

Therefore, in the brightness enhancement film of a type that transmits alinearly polarized light having the above-mentioned predeterminedpolarization axis, by arranging the polarization axis of the transmittedlight and entering the light into a polarizing plate as it is, theabsorption loss by the polarizing plate is controlled and the polarizedlight can be transmitted efficiently. On the other hand, in thebrightness enhancement film of a type that transmits a circularlypolarized light as a cholesteric liquid-crystal layer, the light may beentered into a polarizer as it is, but it is desirable to enter thelight into a polarizer after changing the circularly polarized light toa linearly polarized light through a retardation plate, taking controlan absorption loss into consideration. In addition, a circularlypolarized light is convertible into a linearly polarized light using aquarter wavelength plate as the retardation plate.

A retardation plate that works as a quarter wavelength plate in a widewavelength ranges, such as a visible-light band, is obtained by a methodin which a retardation layer working as a quarter wavelength plate to apale color light with a wavelength of 550 nm is laminated with aretardation layer having other retardation characteristics, such as aretardation layer working as a half-wavelength plate. Therefore, theretardation plate located between a polarizing plate and a brightnessenhancement film may consist of one or more retardation layers.

In addition, also in a cholesteric liquid-crystal layer, a layerreflecting a circularly polarized light in a wide wavelength ranges,such as a visible-light band, may be obtained by adopting aconfiguration structure in which two or more layers with differentreflective wavelength are laminated together. Thus a transmittedcircularly polarized light in a wide wavelength range may be obtainedusing this type of cholesteric liquid-crystal layer.

Moreover, the polarizing plate may consist of multi-layered film oflaminated layers of a polarizing plate and two of more of optical layersas the above-mentioned separated type polarizing plate. Therefore, apolarizing plate may be a reflection type elliptically polarizing plateor a semi-transmission type elliptically polarizing plate, etc. in whichthe above-mentioned reflection type polarizing plate or a transflectivetype polarizing plate is combined with above described retardation platerespectively.

Although an optical film with the above described optical layerlaminated to the polarizing plate may be formed by a method in whichlaminating is separately carried out sequentially in manufacturingprocess of a liquid crystal display etc., an optical film in a form ofbeing laminated beforehand has an outstanding advantage that it hasexcellent stability in quality and assembly workability, etc., and thusmanufacturing processes ability of a liquid crystal display etc. mayberaised. Proper adhesion means, such as an adhesive layer, may be usedfor laminating. On the occasion of adhesion of the above describedpolarizing plate and other optical films, the optical axis may be set asa suitable configuration angle according to the target retardationcharacteristics etc.

A method for producing the antistatic pressure-sensitive adhesiveoptical film according to the present invention will be describedhereinafter.

For example, an application liquid containing a conductive polymer and asulfonic acid compound is applied to the optical film 1 described above,and dried to form an antistatic layer 2. The solid concentration of theapplication liquid is preferably adjusted to approximately 0.5 to 5% byweight. Firstly, the application liquid is applied to the optical film 1using application methods, roll coating methods such as a reversecoating and a gravure coating; a spin coating method; a screen coatingmethod; a fountain coating method; a dipping method; a spray method,etc., and then dried to obtain an antistatic layer.

The thickness of the antistatic layer is preferably 5 to 1000 nm. Inconsideration of optical property deterioration, the thickness of theantistatic layer is usually 5000 nm or less. Thicker antistatic layersmay easily cause possible breakage within the antistatic layer due toinsufficient strength of the antistatic layer, and may not providesufficient adhesion. The thickness of the antistatic agent is 500 nm orless, preferably 300 nm or less, and more preferably 200 nm or less. Inconsideration of guarantee of adhesion, and suppression of peelingelectrification, the thickness is 5 nm or more, and preferably 10 nm ormore. On the other hand, the thicker antistatic layer gives the morepreferable suppression effect of peeling electrification, but thethickness exceeding 200 nm can only give the same or less in suppressioneffect of peeling electrification. In consideration of such a point, thethickness is 5 to 500 nm, preferably 10 to 300 nm, and more preferably10 to 200 nm.

In formation of the antistatic layer 2, an activation treatment maybeperformed with respect to the optical film 1. As the activationtreatment, various methods, for example, corona treatment, low-pressureUV treatment, plasma treatment, etc., are employable. When using anaqueous solution containing an electric conductive polymer as anantistatic agent, the activation treatment is effective, and cansuppress repelling of the aqueous solution in application. Theactivation treatment is especially effective, when the optical film 1 isof polyolefin-based resin and norbornene-based resin.

Formation of the pressure-sensitive adhesive layer 3 is performed bylamination onto the above-mentioned antistatic layer 2. Formationmethods are not especially limited, and there may be adopted: a methodin which a pressure-sensitive adhesive solution is applied onto anantistatic layer, and then is dried; and a method of transfer using areleasing sheet having a pressure-sensitive adhesive layer formedthereon etc. A thickness of the pressure-sensitive adhesive layer is notespecially limited; it is preferably about 10 to 40 μm.

As components of the releasing sheet, there may be mentioned suitablesheeted materials: papers; synthetic resin films, such as polyethylenes,polypropylenes, and polyethylene terephthalates; rubber sheets; papers;cloths; nonwoven fabrics; nets; foamed sheets; metallic foils; andlaminated materials of the above-mentioned materials, etc. In order toincrease releasability from the pressure-sensitive adhesive layer 3,releasing treatment giving low adhesive properties, such as asiliconization, a long chain alkyl treatment, and a florine treatment,may be performed to a surface of the releasing sheet if needed.

In addition, in the present invention, ultraviolet absorbing propertymay be given to the above-mentioned each layer, such as antistaticpressure-sensitive adhesive optical film, an optical film etc. and anadhesive layer, using a method of adding UV absorbents, such assalicylic acid ester type compounds, benzophenol type compounds,benzotriazol type compounds, cyano acrylate type compounds, and nickelcomplex salt type compounds.

The adhering strength between the antistatic layer 2 and thepressure-sensitive adhesive layer 3 preferably has a peeling angle of180° C., and it preferably has adhering strength of 18 N/25 mm or moreat a peeling rate of 300 mm/min, and more preferably 20 N/25 mm or more.The adhering strength less than 18N/25 mm may cause adhesive residue inthe case of peeling of the optical film from the liquid crystal panel,leading to possible peeling under heated condition and wet and heatedcondition.

An antistatic pressure-sensitive adhesive optical film of the presentinvention may be preferably used for manufacturing various equipment,such as liquid crystal display, etc. Assembling of a liquid crystaldisplay may be carried out according to conventional methods. That is, aliquid crystal display is generally manufactured by suitably assemblingseveral parts such as a liquid crystal cell, optical films and, ifnecessity, lighting system, and by incorporating driving circuit. In thepresent invention, except that the optical film by the present inventionis used, there is especially no limitation to use any conventionalmethods. Also any liquid crystal cell of arbitrary type, such as TNtype, and STN type, π type may be used.

Suitable liquid crystal displays, such as liquid crystal display withwhich the above-mentioned antistatic pressure-sensitive adhesive opticalfilm has been located at one side or both sides of the liquid crystalcell, and with which a backlight or a reflector is used for a lightingsystem may be manufactured. In this case, the antistaticpressure-sensitive adhesive optical film by the present invention may beinstalled in one side or both sides of the liquid crystal cell. Wheninstalling the optical films in both sides, they may be of the same typeor of different type. Furthermore, in assembling a liquid crystaldisplay, suitable parts, such as diffusion plate, anti-glare layer,antireflection film, protective plate, prism array, lens array sheet,optical diffusion plate, and backlight, may be installed in suitableposition in one layer or two or more layers.

Subsequently, organic electro luminescence equipment (organic ELdisplay) will be explained. Generally, in organic EL display, atransparent electrode, an organic emitting layer and a metal electrodeare laminated on a transparent substrate in an order configuring anilluminant (organic electroluminescence illuminant) Here, an organicemitting layer is a laminated material of various organic thin films,and much compositions with various combination are known, for example, alaminated material of hole injection layer comprising triphenylaminederivatives etc., an emitting layer comprising fluorescent organicsolids, such as anthracene; a laminated material of electronic injectionlayer comprising such an emitting layer and perylene derivatives, etc.;laminated material of these hole injection layers, emitting layer, andelectronic injection layer etc.

An organic EL display emits light based on a principle that positivehole and electron are injected into an organic emitting layer byimpressing voltage between a transparent electrode and a metalelectrode, the energy produced by recombination of these positive holesand electrons excites fluorescent substance, and subsequently light isemitted when excited fluorescent substance returns to ground state. Amechanism called recombination which takes place in an intermediateprocess is the same as a mechanism in common diodes, and, as isexpected, there is a strong non-linear relationship between electriccurrent and luminescence strength accompanied by rectification nature toapplied voltage.

In an organic EL display, in order to take out luminescence in anorganic emitting layer, at least one electrode must be transparent. Thetransparent electrode usually formed with transparent electricconductor, such as indium tin oxide (ITO), is used as an anode. On theother hand, in order to make electronic injection easier and to increaseluminescence efficiency, it is important that a substance with smallwork function is used for cathode, and metal electrodes, such as Mg—Agand Al—Li, are usually used.

In organic EL display of such a configuration, a very thin film about 10nm forms an organic emitting layer in thickness. For this reason, lightis transmitted nearly completely through organic emitting layer asthrough transparent electrode. Consequently, since the light thatenters, when light is not emitted, as incident light from a surface of atransparent substrate and is transmitted through a transparent electrodeand an organic emitting layer and then is reflected by a metalelectrode, appears in front surface side of the transparent substrateagain, a display side of the organic EL display looks like mirror ifviewed from outside.

In an organic EL display containing an organic electro luminescenceilluminant equipped with a transparent electrode on a surface side of anorganic emitting layer that emits light by impression of voltage, and atthe same time equipped with a metal electrode on a back side of organicemitting layer, a retardation plate may be installed between thesetransparent electrodes and a polarizing plate, while preparing thepolarizing plate on the surface side of the transparent electrode.

Since the retardation plate and the polarizing plate have functionpolarizing the light that has entered as incident light from outside andhas been reflected by the metal electrode, they have an effect of makingthe mirror surface of metal electrode not visible from outside by thepolarization action. If a retardation plate is configured with a quarterwavelength plate and the angle between the two polarization directionsof the polarizing plate and the retardation plate is adjusted to π/4,the mirror surface of the metal electrode may be completely covered.

This means that only linearly polarized light component of the externallight that enters as incident light into this organic EL display istransmitted with the work of polarizing plate. This linearly polarizedlight generally gives an elliptically polarized light by the retardationplate, and especially the retardation plate is a quarter wavelengthplate, and moreover when the angle between the two polarizationdirections of the polarizing plate and the retardation plate is adjustedto π/4, it gives a circularly polarized light.

This circularly polarized light is transmitted through the transparentsubstrate, the transparent electrode and the organic thin film, and isreflected by the metal electrode, and then is transmitted through theorganic thin film, the transparent electrode and the transparentsubstrate again, and is turned into a linearly polarized light againwith the retardation plate. And since this linearly polarized light liesat right angles to the polarization direction of the polarizing plate,it cannot be transmitted through the polarizing plate. As the result,mirror surface of the metal electrode may be completely covered.

EXAMPLE

The present invention will be described specifically with reference toexamples hereinafter, but the present invention is not limited by theseexamples. Both of parts and % in each example are based on weight.

(Production of Polarizing Plate)

A polyvinyl alcohol film having a thickness of 80 μm was stretched 5times in a 40° C. iodine aqueous solution, and subsequently was driedfor 4 minutes at 50° C. to obtain a polarizer. A triacetyl cellulosefilm was adhered on both sides of this polarizer using a polyvinylalcohol-based pressure-sensitive adhesive to obtain a polarizing plate.

Example 1 (Formation of Antistatic Layer)

An aqueous solution (0.8% of solid content) containing 3 parts ofpoly(3,4-ethylene dioxythiophene) as a conductive polymer, 100 parts ofa polyester resin as a binder component, and 5 parts of polystyrenesulfonic acid was prepared. The aqueous solution concerned was appliedto one side of the polarizing plate so that the thickness after dryingmight give 80 nm, and the applied layer was dried by heating for 2minutes at 80° C., and an antistatic layer was formed.

(Formation of a Pressure-Sensitive Adhesive Layer)

An amount of 95 parts of butyl acrylate, 15 parts ofN-cyclohexylmaleimide, 5 parts of hydroxyethyl acrylate, and 0.2 partsof benzoyl peroxide were dissolved in 300 parts of toluene as a basepolymer, the reaction was continued at about 60° C. for 6 hours underagitation. Thus, a solution (25% of solid content) containing anacryl-based polymer containing nitrogen with a weight average molecularweight of 2 million was prepared. As an isocyanate-based cross-linkingagent, 0.5 part of Coronate L manufactured by NIPPON POLYURETHANEINDUSTRY CO., LTD., with respect to 100 parts of polymer solid contentwas added to the above-described solution of the acryl-based polymercontaining nitrogen to obtain a pressure-sensitive adhesive solution(12% of solid content). The pressure-sensitive adhesive solutionconcerned was applied by a reverse roll coating method to a releasesheet (product made by MITSUBISHI POLYESTER FILM CORPORATION, DIAFOILMRF38, polyethylene terephthalate base material) so as to have athickness after dried of 25 μm. Subsequently, a release sheet wasfurther given on the applied solution, the material obtained was driedin hot air circulating oven, and a pressure-sensitive adhesive layer wasformed.

(Production of an Antistatic Pressure-Sensitive Adhesive Optical Film)

The release sheet having the pressure-sensitive adhesive layer formedthereon was attached on the antistatic layer of the above-describedantistatic polarizing plate. The obtained sheet was aged for one week ata room temperature, and an antistatic pressure-sensitive adhesivepolarizing plate was thus obtained.

Example 2

Except for having used 5 parts of N-phenylmaleimide instead ofN-cyclohexylmaleimide in formation of the pressure-sensitive adhesivelayer in Example 1, an antistatic pressure-sensitive adhesive polarizingplate was produced by the same method as in Example 1.

Example 3

Except for having used 25 parts of N-acryloyl morpholine instead ofN-cyclohexylmaleimide in formation of the pressure-sensitive adhesivelayer of Example 1, an antistatic pressure-sensitive adhesive polarizingplate was produced by the same method as in Example 1.

Example 4

Except for having used 3 parts of polystyrene sulfonic acid in formationof the antistatic layer of Example 1, an antistatic pressure-sensitiveadhesive polarizing plate was produced by the same method as in Example1.

Example 5

Except for having used 7.5 parts of polystyrene sulfonic acid information of the antistatic layer of Example 1, an antistaticpressure-sensitive adhesive polarizing plate was produced by the samemethod as in Example 1.

Comparative Example 1

Except for not having used N-cyclohexylmaleimide in formation of thepressure-sensitive adhesive layer of Example 1, an antistaticpressure-sensitive adhesive polarizing plate was produced by the samemethod as in Example 1.

Comparative Example 2

Except for not having formed an antistatic layer in Example 1, apressure-sensitive adhesive polarizing plate was produced by the samemethod as in Example 1.

Following evaluations were performed about the antistaticpressure-sensitive adhesive optical films obtained by Examples andComparative examples. Table 1 illustrates evaluation results.

[Adhesion]

The produced antistatic pressure-sensitive adhesive optical films werecut into pieces with 25 mm width×50 mm length. A side of thepressure-sensitive adhesive layer and was attached to a vapor-depositedside of a vapor deposition film obtained by vacuum deposition of indiumtin oxide on a surface of a polyethylene terephthalate film having athickness of 50 μm, and was kept standing under conditions of 23°C.C/60% RH for 20 minutes or more. Subsequently, the edge of thepolyethylene terephthalate film was peeled by hand, adhesion of thepressure-sensitive adhesive on the side of the polyethyleneterephthalate film was confirmed, and the adhering strength 180° peeling(N/25 mm) between the antistatic layer and the pressure-sensitiveadhesive layer was evaluated for using a tensile testing machine (madeby Shimadzu Corp., AUTOGRAPH AG-1), under a room temperature atmosphere(25° C.) at a speed of testing of 300 mm/min.

[Water Resistance] (Warm Water Immersion)

The produced antistatic pressure-sensitive adhesive optical film was cutinto a size of 100 mm×100 mm to obtain a sample. The pressure-sensitiveadhesive layer of the sample was attached to an alkali free glass (madeby Dow Corning Corporation) and was immersed in 40° C. warm water for 10hours for evaluation of peeling by visual inspection.

[Antistatic Effect]

The produced antistatic pressure-sensitive adhesive optical film was cutinto a size of 100 mm×100 mm, and was attached on a liquid crystalpanel. This panel was placed on a backlight having a luminance of 10000cd, and static electricity of 5 kv was applied using an ESD (productmade by SANKI Co., Ltd., ESD-8012A) as a static electricity generator tocause alignment disorder of the liquid crystal. The recovery period oftime (second) of the display defect by the alignment defect was measuredfor using an instantaneous multi-photometry detector (made by OTSUKAELECTRONICS CO., LTD., MCPD-3000).

TABLE 1 Display defect Adhering strength recovery period of (N/25 mm)Water resistance time (s) Example 1 22 Peeling not <1 observed Example 220 Peeling not <1 observed Example 3 23 Peeling not <1 observed Example4 20 Peeling not <1 observed Example 5 22 Peeling not <1 observedComparative 15 Peeling observed <1 Example 1 Comparative 13 Peeling not600< Example 2 observed

1. An antistatic pressure-sensitive adhesive optical film, the opticalfilm having an antistatic layer laminated on at least one side of theoptical film, and a pressure-sensitive adhesive layer further laminatedon the antistatic layer, wherein the antistatic layer comprises aconductive polymer and a sulfonic acid compound as raw materialcomponents, and the pressure-sensitive adhesive layer is formed of anacryl-based pressure-sensitive adhesive containing nitrogen.
 2. Theantistatic pressure-sensitive adhesive optical film according to claim1, wherein the conductive polymer is water soluble or water dispersible.3. The antistatic pressure-sensitive adhesive optical film according toclaim 2, wherein the water soluble or water dispersible conductivepolymer is a polythiophene conductive polymer.
 4. The antistaticpressure-sensitive adhesive optical film according to claim 1, wherein abase polymer of the acryl-based pressure-sensitive adhesives containingnitrogen is a copolymer of a monomer containing nitrogen and anacryl-based monomer, or a mixture of a polymer containing nitrogen andan acryl-based polymer.
 5. An image viewing display using at least oneof the antistatic pressure-sensitive adhesive optical film accordingclaim
 1. 6. An image viewing display using at least one of theantistatic pressure-sensitive adhesive optical film according claim 2.7. An image viewing display using at least one of the antistaticpressure-sensitive adhesive optical film according claim
 3. 8. An imageviewing display using at least one of the antistatic pressure-sensitiveadhesive optical film according claim
 4. 9. The antistaticpressure-sensitive adhesive optical film according to claim 1, whereinthe sulfonic acid compound is a water soluble sulfonic acid compound.10. The antistatic pressure-sensitive adhesive optical film according toclaim 1, wherein the antistatic layer comprises 100 to 300 parts byweight of the sulfonic acid compound with respect to 100 parts by weightof the conductive polymer.
 11. The antistatic pressure-sensitiveadhesive optical film according to claim 1, wherein the acryl-basedpressure-sensitive adhesive comprises a copolymer of a monomercontaining nitrogen and an acryl-based monomer, and wherein said monomercontaining nitrogen is a vinyl monomer containing a nitrogen atom. 12.The antistatic pressure-sensitive adhesive optical film according toclaim 1, wherein the acryl-based pressure-sensitive adhesive comprises amixture of a polymer containing nitrogen and an acryl-based polymer. 13.An antistatic pressure-sensitive adhesive optical film comprising: (a)an optical film; (b) an antistatic layer, comprising a conductivepolymer and a sulfonic acid compound as raw material components,laminated on at least one side of the optical film; and (c) apressure-sensitive adhesive layer, comprising an acryl-basedpressure-sensitive adhesive containing nitrogen, laminated on theantistatic layer.